Ladder frames as carriers for the paneling of a motor vehicle body have been known for more than 100 years. Modern, self-supporting motor car bodies frequently also have an underbody with side members and cross members, which, even if they merely have to absorb a part of the structural forces that occur on a motor vehicle, can be considered to be a ladder framework. Such an underbody is known from U.S. Pat. No. 6,540,286 B2. It comprises two side members, which extend over the entire length of the vehicle and are interconnected through a plurality of cross members in the form of cylindrical tubes of a constant cross section. Some of these cross members abut lateral flanks of the side members located opposite one another; others laterally protrude over the side members and are therefore fastened resting on these. The small size of the contact area between the side members and cross members touching one another or crossing one another makes it more difficult to produce a connection that can be subjected to a torsional load.
In the case of the cross member abutting the side member, the torsional load capacity depends on the cross sectional dimensions of the latter. A high load capacity requires large dimensions, which in turn however lead to a high weight of the cross member. A high weight in turn leads to a higher fuel consumption.
There is therefore a need for a motor vehicle underbody which achieves a high load capacity with low weight which can be produced rationally at the same time Furthermore, other desirable features and characteristics of the various embodiments will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.